The effect of certain variables on the tumor and tissue distribution of tracers. II. Carrier effect: rapidity of onset and concentrations necessary for initiation and maximum response.

The smallest quantity of carrier Ga and Mn necessary to initiate and maximize a carrier effect was studied in the Morris 7777 rat hepatoma model. The quantity needed for a maximum response did not appear to adversely effect the rats. Not all tissues were equally affected at the same plasma concentrations. If carrier Ga was administered 2 hours following 67Ga injection and the rats sacrificed 30 minutes later, a dramatic change occurred in background activity, which was more pronounced in healthy than malignant tissues. Early viable and nonviable tumor/background ratios were improved by this technique. The data suggest that the use of carrier Ga and Mn might improve early lesion/background ratios in patients. This could be of use if tumor imaging were undertaken with 68Ga or 52mMn with positron detector systems.